There are 11 candidates on the ballot paper for the first round of voting. That means no-one is likely to get the required 50 per cent for an outright win on Sunday.

The top two candidates after the first round will go through to a run-off vote on May 7.

Normally the only candidates with a chance of finishing in the top two (and making it to the second round) are those from France's two main parties — the Socialists and the Republicans.

But this election is anything but normal. Under the deeply unpopular President Francois Hollande, who had an approval rating of 4 per cent, Socialist support has collapsed and in the final weeks of campaigning it has turned into a four-way race that is simply too close to call.

Three of them are outsiders, two would completely overhaul France's relationship with the world, and the only mainstream contender is under a corruption cloud.

The far-left candidate

The eloquent far-left leader of a movement called La France Insoumise (France Unbowed or Rebellious France) has also threatened "Frexit" and suggested abandoning the euro.

His protectionist economic policies are not far-removed from Ms Le Pen's. Among his ideas are a 32-hour working week, the nationalisation of assets and 100 per cent taxes on personal income over $400,000 euros.

If he and Ms Le Pen were to face off against one another, the race would become even more unpredictable.

Some think it would trigger a financial crisis. At a minimum either candidate could quickly splinter the remaining unity within the European Union.

Mr Macron has probably been the biggest beneficiary of the meltdowns in the mainstream parties and polling puts him on almost level pegging with Ms Le Pen.

His supporters speak endlessly about how disillusioned voters have been captured by his ambitious promises to improve health care and education, and boost unemployment benefits, all while reforming the struggling economy.

But his biggest asset seems to be that he's neither from the far-left or the far-right.

Mr Macron's biggest challenge will be getting through this weekend. He's largely untried, untested and doesn't have the party infrastructure of a typical leading candidate, so there's always a chance his support could slip away at the last moment.

Throughout the campaign there's been a lot of focus on his wife Brigitte, who is his former French teacher and 25 years his senior. The relationship is considered unusual, even in liberal France.